1. Field of the Invention
The present invention relates to the field of burner technology for gas turbines. It relates to a burner arrangement for a gas turbine, comprising at least one burner, which is arranged in the plenum of the gas turbine and leads with an inner injection space into a combustion chamber and to which compressed air is admitted on the outside from a compressor stage of the gas turbine, and also a fuel lance allocated to the burner and intended for the alternative feeding of liquid and/or gaseous fuels, which fuel lance has a central liquid-fuel tube and a pilot-gas tube concentrically surrounding the liquid-fuel tube, the tubes ending in associated outlet openings in a lance head at the tip of the fuel lance, and which fuel lance can be inserted with the lance head into an inner tube, connected to the injection space, of the burner.
Such a burner arrangement is disclosed, for example, by German Offenlegungsschrift DE-A1-43 06 956.
2. Discussion of Background
Combustion chambers having so-called double-cone burners, to which fuel is fed from outside through insertable burner lances (see the publication mentioned at the beginning), have for a long time proved successful for stationary gas turbines in power stations. In this case, the fuel lance is usually designed as a dual fuel lance, i.e. gaseous fuel (pilot gas) and liquid fuel (normally an oil/water mixture) can be fed alternatively in the fuel lance. To this end, appropriate tubes (liquid-fuel tube, pilot-gas tube) are arranged concentrically in the lance and form passages for the gas and the liquid fuel. The passages end at the lance tip (in the lance head) in associated outlet openings for the respective fuel. The lance head of the lance is in a corresponding inner tube of the burner, so that the issuing fuel passes into the injection space adjoining the inner tube.
During normal oil operation, an oil/water mixture flows in the inner liquid-fuel tube (liquid-fuel passage) of the fuel lance. In the starting phase, however, in gas operation, pilot gas flows in the annular pilot-gas passage between the liquid-fuel tube and the pilot-gas tube. Here, one of the two fuel passages is always out of service. Sometimes, even both passages are out of use simultaneously.
Since the requisite positive pressure relative to the injection space of the burner is absent in the passages which are not being used, an ingress of hot gases or hot oil from the burner into the passages which are not being used may occur and may lead to temporary or permanent impairment of the function of the fuel lance. It would therefore be desirable to design the burner arrangement in such a way that such an ingress is reliably prevented in a simple manner.